#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
//using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using i128 = __int128_t;
using u128 = unsigned __int128_t;
using mint = atcoder::static_modint<998244353>;
const int mod = 998244353;
#include <chrono>
mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());
int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1};
int dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};
template<class T>
bool chmin(T& a, const T& b){
    if (b < a){
        a = b;
        return true;
    }
    else { 
        return false;
    }
}
template<class T> 
bool chmax(T& a, const T& b){
    if (a < b){
        a = b;
        return true;
    }
    else {
        return false;
    }
}

void solve(){
    int h, w;
    cin >> h >> w;
    vector<string> s(h);
    for (int i = 0; i < h; i++){
        cin >> s[i];
    }
    for (int i = 1; i <= h; i++){
        for (int j = 1; j <= w; j++){
            vector<vector<bool>> used(h, vector<bool> (w, false));
            bool ok = true;
            for (int a = 0; a < h; a++){
                for (int b = 0; b < w; b++){
                    if (s[a][b] == '#' && !used[a][b]){
                        int x = a + i, y = b + j;
                        if (x >= h || y >= w){
                            ok = false;
                        }
                        else {
                            if (s[x][y] == '#'){
                                used[x][y] = true;
                            }
                            else {
                                ok = false;
                            }
                        }
                    }
                }
            }
            if (ok){
                cout << "YES" << '\n';
                return;
            }
        }
    }
    cout << "NO" << '\n';
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;   
    while(t--){
        cout << fixed << setprecision(15);          
        solve();
    }   
}